OK, I found an ad for the table version. I'll send it to Brad.

Hi Robert,
I saw this on Radio Museum during my search, there was no information at all, https://www.radiomuseum.org/r/airzone_all_electric_2.html#c

Hi Rudolf,

Yes that's the advert I sent to Brad. Looking at your chassis I'm sure it is a variation of the Airzone. I'd recommend you keep searching for info on early Airzone sets. You will find pictures of the earlier cub chassis online, although I couldn't find one the same as yours. The unusual station dial on your set is shared with the cathedral set - I've been trying to find one to complete my own cub - they are very hard to find. I will end up making one. Good luck with the restoration.

Robert

Hi Robert,
You're could be right about the speaker, what sort of speaker would have been used ? I've done more research on it and I'm sure this is the type described here, https://www.innerfidelity.com/content/how-balanced-armature-receiversdrivers-work
There are 3 controls in this radio, the tuning - the sensitivity on the RH and out of sight is a variable ant. tap control, there is no volume control. There is one more control on the back of the speaker box, marked on is "Blue Spot", I guess that is what controls the vibration of the reed which in turn controls the speaker cone movement.
Your thoughts would be appreciated as this early vintage is new to me.

I meant to ask you , how is the volume level on your AC controlled ?

Photo uploaded to Post 18.

Hi Rudolph,

The variable capacitor is the reaction control and was used for volume control. Also the antenna tap would reduce the signal strength by selecting different taps on the antenna coil - so it would also have an effect on signal volume. Both controls work together in a fairly crude but effective way.
You are correct about the speaker - it is a balanced armature type. The control on the back will work a bit like a tone control - and will also affect volume. These speakers are from the mid to late 20s. The correct speaker for your set will be an electrodynamic type - with the field coil used in the filtering for the B+ (main high voltage for the set). The speaker will also have a mounted transformer for matching the output valve impedance. If you want some pictures of my set, and the speaker, send me an email: robert.mcgregorwestvic.com.au

Robert

There is a description of that speaker in probably Electronics Australia but definitely In Aurthur (?) Cushens Vintage Radio book. I have a copy.

That was the speaker type that pre dated the Rice-Kellogg one, which was the field coil version of what we have today. What you have is a "Rocking armature" which prevailed in the microphone of telephones.

Whist I rarely do it, one could remove the internals of that cap & put a 1μF NP in it (re-stuff), or just cut it out of circuit & find a place for a modern on in the pan . Do check "Frank's Electron Tube Pages" { http://www.tubedata.info/ } for valve info,

If you can get dimensions & the rest is OK. There are examples where a guy has managed to get another with a printer to make replacements for some "Pot Metal" (aka Die cast) bits. Its a cheap easy metal to work with & was used to make a whole range of stuff & used as stupidly as possible: It was all about cost. Some clown made the tongue of the MKII Zephyr's glove box lid out of it. Interesting work of art with an angle grinder, making a new one: Its still working.

I have a turntable here that the motor housing looks like your speaker (idiotic use of it) and the inertia wheels on some dial drives, were it. They also exfoliated & fell to bits. Araldite saved some: The lathe here often turns out replacements.

Marc

Hi Robert,
I paid a bit more attention to the description in the advert with regards to "loud speaker", apparently there is provision for both magnetic and dynamic speakers. That's probably why there are so many connections on the back of the radio. The only way I'll find out is to try to draw out the circuit.
I'd love pictures of your radio, I think you know my e-mail rtfeld41tpg.com.au I'm the one with the AWA Radiola 4
Cheers
Rudy

Thanks Marcc,
There is also a description on Radio Museum which is quite informative,

https://www.radiomuseum.org/forum/the_development_of_the_loudspeaker.html

I have a publication from HRSA by Ray Kelly (a founder member) called HRSA Loudspeaker Notebook, 3rd Edition, 1993.

This lists many speaker manufacturers of the early days, categorised into Brand Name, Construction and Country of Origin.

Construction categories are horn, cone, moving coil, dynamic and cabinet. It does not say what the working mechanism in the cabinets is. Most cones appear to be armature movement speakers like the speaker in this thread. I have trawled right through the book and it does not have a picture of the speaker in this thread, so here is a list of the posibilities:

AEG cabinet
Blue Spot (Blaupunkt) cone, cabinet
Delmonte (Grawor) cone
Hegra cone
Lauritznudsen cone
Loewe (Loewe Radio) cone
Siemens cone
Tefag cone
Tekefunken cone

If I had to take a punt I would say Loewe, only because they made plain rectangular cabinets without any additional fancy molding.

I see that there is decoration on the end of the adjusting knob of the speaker in this thread, that does not show up clearly in the photograph. This might be a clue.

The book is mostly compiled of copies of advertisments. Many show proudly pictures of their working mechanism. So a good photo of the working mechanism may be helpful in identification.

Photo uploaded to Post 26.

Bluespot it is which I missed in post 19 above. One of the ads in my HRSA book infers British made, though Blaupunkt and Point Bleue names are also used for German and French markets.

Hi Rudy,

I tried sending you a couple of emails - but it doesn't go through. I think your email is incorrect? and I don't have your old one (computer crash a while ago and I lost everything). I might be easier to send me a test: robert.mcgregorwestvic.com.au
Robert

It is a Blaupunkt, "IDEAL" on the knob confirms it.

"History. Founded in 1923 in Berlin as "Ideal," the company was acquired by Robert Bosch AG in 1933. In 1938 it changed its name to

"Blaupunkt", German for "blue point" or "blue dot", after the blue dot painted onto its headphones that had passed quality control.

Blaupunkt - Wikipedia"